This invention relates to measuring apparatus, and more particularly to apparatus for measuring the deflection of a member such as a saw blade upon a given increase in force being applied thereto.
In the slicing of an elongated, generally cylindrical silicon ingot into individual wafers, it is well known to provide a rotary saw blade having a central opening defined by a circular inner edge, that edge actually being the cutting edge of the saw blade. The ingot is positioned through the opening, the saw blade is rotated, and the saw blade is further moved generally laterally of the longitudinal axis of the ingot so that the cutting edge contacts and cuts through and across the ingot.
It is to be understood that proper blade tension is of the utmost importance during the slicing operation. Toward this end, the blade should be highly tensioned, yet is must be understood that such a blade has a yield point, i.e., that point beyond which further force applied to the blade so as to increase blade tension actually permanently stretches the material. It has been found highly advantageous to increase such force to a point just short of that yield point. This results in a very high tension of the blade, but without any permanent deformation thereof.
Heretofore, a judgment as to the blade tension has been made by the operator of the apparatus increasing the tension thereof, and then judging by manual contact with the blade the degree of tension of the blade. Obviously such a system presents certain problems, due to the relatively inexact nature of the measurement.